Dietary restriction (DR), or limited food intake without malnutrition, is known to protect against several age- related disorders and extends lifespan in many organisms, including mammals. However, the cellular and molecular mechanisms underlying this fascinating phenomenon remain poorly understood. We recently identified a critical role for the process of autophagy in the lifespan extension induced by DR in C. elegans (Hansen et al., PLoS Genetics, 2008). Autophagy is a conserved pathway by which cellular components are degraded and recycled. Specifically, we found that autophagy is induced in response to DR, and this induction is dependent on the FOXA transcription factor PHA-4, a known regulator of DR-induced longevity. Accordingly, we and others have found that several genes with functions in autophagy are required for these animals to live long. While establishing an important link between autophagy and the longevity response to DR, these studies did not address how DR induces autophagy at the cellular and molecular level to extend the lifespan of the organism. In particular, it remains unknown how the autophagy process contributes to organismal aging in terms of which tissues are critical, and what signaling machinery is engaged to select cellular components as cargo for degradation in response to DR. The goal of this application is to use genetic and biochemical approaches to characterize in which tissues autophagic turn-over is induced to affect longevity in adult C. elegans subjected to DR, as well as to identify novel regulators of autophagy with effects on longevity. Specifically, in Aim 1, we will use imaging techniques like TEM and develop new fluorescent reporters to detect autophagic events <as well as the identity of the cytoplasmic cargo>in different tissues of aging worms. In Aim 2, we will examine in which tissues autophagy genes functions to modulate longevity, e.g., by tissue-specific, over-expression experiments. Finally, in Aim 3, we will characterize the genetic requirements for autophagy to increase lifespan by DR, and search for new modulators of autophagy, including factors important for autophagic cargo recognition in biochemical and genetic screens. Throughout these studies we will compare the DR longevity model to other longevity pathways that similarly rely on autophagy to extend lifespan, including the daf-2/insulin/IG-1 signaling pathway. Like DR, autophagy plays critical roles in many diseases, including age-related disorders like cancer and neurodegeneration. Understanding the regulation of autophagy and the conserved mechanisms linking autophagy and DR in multicellular organisms like C. elegans are likely to provide new important insights not only into aging but also help developing treatments for such age-related diseases. PUBLIC HEALTH RELEVANCE: The US population of elderly people is rapidly growing and age-related diseases constitute a major health issue in our society. However, the cellular and molecular basis of aging and age-related disorders is poorly understood. This proposal aims to determine how autophagy - a cellular process of cytoplasmic degradation with major biological functions - modulates organismal aging. The proposed research has relevance to public health, because the mechanisms to be investigated are evolutionary conserved and the findings might ultimately provide therapies to treat aging-related diseases.